Pardon my ignorance, but what exactly do you mean by "fuel trims"? If you mean the AFR, then what I'm noticing is it used to settle out perfectly to about 14.7 at idle. But now when I go from throttle (even very light throttle) to neutral, it pegs to 16.0 and stays there for a minute or two, then bounces its way around back to about 14.9... But even then it fluctuates quite a bit for idle. Sometimes back up to 15.6-15.8.
It's like it can't figure out what it's supposed to be doing. And the weird thing is, it appears to throw the codes when I go to a neutral idle, which coincidentally is when the wide band pegs lean as well. Under heavy throttle it appears to dump fuel just fine. So weird. I wonder if it's a bad or dirty MAF. I've tried to clean it once with a q-tip but I'm not sure how you're supposed to clean them exactly.
I have not cleaned the O2. What do you clean it with? For the time being I was assuming it was reading correctly since I was also getting lean codes for both banks. But if that a common thing that causes these two symptoms I'll certainly try that.
Is it possible this is as simple as a stopped up fuel filter?
Fuel trims can be seen in datalog monitoring. If you hook up your handheld and monitor the datalog, you should see short term 1 & 2 and long term 1 & 2. 1.00 is the ideal fuel trim for both banks (which are the upstream O2 readings) 1.00 means the computer is happy with what it has for fuel being delivered and the tune is spot on. +/- 5% is also acceptable. +/- 10% means the ECU is having to add or remove that much fuel trim to hit the target AFR. If short term banks 1 & 2 don't match each other within 1-2% you may have an O2 or other fuel issue. Say bank 1 says .85 and bank 2 says 1.00. Since you can't tune a 3v bank to bank like a Coyote, the ECU is going to side on caution and use the fuel trim for .85 as best it can to keep target AFR. This could cause your AFR readings to SNAFU. But in either case, it points to a fuel issue. O2's, injectors, fuel filter, or tune.
As far as cleaning the MAF, it's highly preferred to spray clean the MAF with electrical parts cleaner or "MAF" cleaner. Carb cleaner works just as well. I've even used brake parts cleaner in pinch. You don't want to swab it as you could damage the element and/or leave behind particulates that could interfere with MAF function. You could do a datalog of a 4th gear WOT pull, maybe 2k/rpm to 4k/rpm if you wanted to be "safe" and input the log on your computer, download livelink from SCT and check the MAF readings. If it plots a smooth graph line, I doubt it's the MAF malfunctioning or being dirty. If it's jagged and funky, you could have a MAF problem.
As stated already, you can clean your O2's by using a torch. Personally I soak my O2's in CRC Electrical parts cleaner over-night. Swish it around once in a while so the fluid moves throughout the fins. This usually breaks up the majority of any carbon build up. After that I let it air dry, and THEN I hit it with the torch and check resistance. It's not so much the resistance as it is how fast it reacts. Once you heat it evenly, breaking down any remaining carbons/contaminants, you should be able to watch your ohm meter (if yours response fast enough) and see 1/10th of a second reactions when you hit it with the flame a few times.
Our upstream O2's are heated, so it's still possible you could clean the sensors and still have issues if the heating elements are bad, only way to know is to try. Personally I'll always try to clean my O2's before I junk them. I can't stand spending $70-$90 on O2 sensors. Pisses me off just thinking about it.
